Method for the continuous hydroformmylation of polyakenes having 30 to 700 carbon atoms

ABSTRACT

Essentially monounsaturated polyalkylenes having from 30 to 700 carbon atoms are continuously hydroformylated by a process in which i) a hydroformylation-active cobalt carbonyl catalyst is prepared from a catalyst precursor dissolved in an aqueous phase in the absence of the polyalkylenes, ii) the polyalkylenes are hydroformylated by means of synthesis gas in the presence of the cobalt carbonyl catalyst in a reaction zone, iii) the cobalt carbonyl catalyst is separated from the output from the reaction zone with at least partial reformation of the catalyst precursor and the catalyst precursor is recirculated to step i).

[0001] The present invention relates to a process for the continuoushydroformylation of essentially monounsaturated polyalkenes having from30 to 700 carbon atoms.

[0002] Polybutenylamines are valued fuel and lubricant additives. Theyare advantageously prepared by hydroformylation of polybutene orpolyisobutene and subsequent Mannich reaction or hydrogenative aminationof the oxo product.

[0003] EP 244 616 describes a process for preparing polybutylamines andpolyisobutylamines and illustrates a batchwise hydroformylation ofpolybutene using cobalt octacarbonyl on a laboratory scale.

[0004] WO 90/05711 relates to a 1-hydroxymethylpolyolefin obtainable byhydroformylation of a polyolefin. In an example, the batchwisehydroformylation of polybutene is illustrated on a laboratory scaleusing a cobalt carbonyl catalyst.

[0005] M. Di Serio et al., J. Mol. Catal. 69 (1991) 1-14, describekinetic studies on the hydroformylation of polyisobutene. Thehydroformylation experiments were carried out in the batch mode usingcobalt acetylacetonate.

[0006] WO 95/24431 describes polyolefins having terminal aldehyde orhydroxyl substituents and derivatives thereof, e.g. alkylaminoderivatives. The latter are obtainable by aminomethylation orhydroformylation and reductive amination. A batchwise hydroformylationof an ethylene-propylene-dicyclopentadiene terpolymer using Co₂(CO)₈ isillustrated on a laboratory scale.

[0007] A continuous hydroformylation process is desirable for economicalindustrial-scale production of oxo products of polyalkylenes. To achievethis, it is necessary to separate the cobalt catalyst from thehydroformylation products and, if necessary after chemicaltransformation, to return it to the hydroformylation reaction. Thecatalyst homogeneously dissolved in the hydroformylation products isparticularly advantageously separated off by making it heterogeneous,for example by converting it into a water-soluble form and extracting itinto an aqueous phase. The water-soluble form is then converted backinto the active catalyst.

[0008] A continuous process of this type is disclosed in WO 98/12235.Here, a polyisobutene-containing organic phase and an acidic aqueouscobalt formate solution are introduced simultaneously into ahydroformylation reactor. After the reaction, the reaction mixture isdepressurized and the cobalt catalyst is recovered by extraction with anaqueous acidic solution in the presence of atmospheric oxygen and apolymeric emulsion breaker. In the process described in WO 98/12235, thein-situ formation of the cobalt catalyst, the extraction of the cobaltcatalyst into the organic phase and the hydroformylation of thepolyalkylene take place in one step in the reaction zone underhydroformylation conditions.

[0009] It has become evident that the selectivity of the known processesin respect of the desired products polyalkylenealdehyde, polyalkylenealcohol and/or polyalkylene ester at a given reactor throughput or thepermissible reactor throughput without loss of selectivity are in needof improvement.

[0010] We have now, surprisingly, found that a high space-time yieldtogether with a high selectivity to the desired product is achieved inthe continuous hydroformylation of polyalkylenes when formation of thecatalyst is carried out beforehand, i.e. outside the hydroformylationzone.

[0011] This finding is surprising since it may be assumed that thein-situ formation of the catalyst proceeds sufficiently rapidly underthe conditions of the hydroformylation of polyalkylenes and, in view ofthe relatively low double bond concentration in the polyalkylenescompared to low molecular weight olefins, there is sufficient catalystavailable in the hydroformylation zone. However, the in-situ catalystformation obviously involves the formation, as intermediates, of lowoxidation state cobalt compounds which display a catalytic activity ofunsatisfactory selectivity and, for example, promote the hydrogenationof the polyalkylenes as against the1-hydro-2-carboaddition(hydroformylation).

[0012] DE-OS 2139630 describes a process for preparing predominantlystraight-chain aldehydes by hydroformylation of olefinically unsaturatedcompounds having from 2 to 20 carbon atoms, in which aqueous cobalt saltsolutions are treated with carbon monoxide and hydrogen in a first step,the aqueous solution is then extracted with an organic phase in a secondstep and the organic phase and a mixture of carbon monoxide and hydrogenare transferred to a third step where, optionally after introduction ofthe olefinically unsaturated compounds if none or only part of thesehave been used for the extraction in the second step, thehydroformylation is carried out. Application of this process to thehydroformylation of polyalkylenes was far from obvious, since DE 2139630is expressly directed at linear aldehydes, while polyalkylenes (and thealdehydes obtained therefrom) are always moderately to stronglybranched.

[0013] The present invention provides a process for the continuoushydroformylation of essentially monounsaturated polyalkylenes havingfrom 30 to 700 carbon atoms, in which

[0014] i) a hydroformylation-active cobalt carbonyl catalyst is preparedfrom a catalyst precursor dissolved in an aqueous phase in the absenceof the polyalkylenes,

[0015] ii) the polyalkylenes are hydroformylated by means of synthesisgas in the presence of the cobalt carbonyl catalyst in a reaction zone,

[0016] iii) the cobalt carbonyl catalyst is separated from the outputfrom the reaction zone with at least partial reformation of the catalystprecursor and the catalyst precursor is recirculated to step i).

[0017] Suitable polyalkylenes have from 30 to 700 carbon atoms, inparticular from 40 to 400 carbon atoms. The polyalkylenes are preferablyoligomers or polymers of C₂-C₆-alkenes, in particular C₃-C₆-alkenes,especially C₃-C₄-alkenes, with the oligomers or polymers havingessentially one olefinic double bond. Particularly suitablepolyalkylenes are polymers of butene or isobutene, especially thosecontaining at least 50% of terminal double bonds in the form of vinyl orvinylidene groups. Suitable polyisobutenes are disclosed, for example,in DE-A 27 02 604 or U.S. Pat. No. 5,286,823.

[0018] Catalyst precursors which can be used are, in particular,water-soluble cobalt(II) salts and salts of the cobalt tetracarbonylanion.

[0019] Suitable cobalt(II) salts are, in particular, cobalt(II)carboxylates, such as cobalt formate, cobalt acetate or cobaltethylhexanoate, and also cobalt acetylacetonate. Thehydroformylation-active cobalt carbonyl catalyst can be prepared from anaqueous cobalt(II) salt solution by reaction with synthesis gas.

[0020] The conversion of the Co²⁺ from the aqueous cobalt(II) saltsolution into a hydroformylation-active cobalt carbonyl catalyst, i.e.hydridocobalt carbonyl, occurs according to the reaction equation:

2Co²⁺+8CO+3H₂→2HCo(CO)₄+4H⁺

[0021] The equation shows that preparation of the catalyst requires asynthesis gas in which CO and H₂ are present in a ratio of 8:3. Since,however, a higher concentration of H₂ has no adverse effect on thereaction, it is advantageous to carry out the preparation of thecatalyst from the aqueous cobalt(II) salt solution using the samesynthesis gas as is also used for the hydroformylation reaction so asnot to have to handle different gas streams. The aqueous cobalt(II) saltsolution is generally treated with synthesis gas at from 50 to 150° C.,preferably from 80 to 120° C., and a pressure from 50 to 400 bar,preferably from 200 to 300 bar. The synthesis gas can comprise from 10to 90% of CO and from 90 to 10% of H₂, preferably from 30 to 70% of COand from 70 to 30% of H₂. The aqueous cobalt(II) salt solution ispreferably brought to a pH of from about 2 to 5, preferably from 3 to 4.The adjustment of the pH can be carried out using, for example, formicacid or acetic acid. The cobalt concentration in the aqueous solution isgenerally from 0.5 to 2% by weight, preferably from 1.1 to 1.7% byweight.

[0022] Apparatuses suitable for the reaction of the cobalt(II) saltsolution with the synthesis gas are customary apparatuses for gas/liquidreactions, for example stirred vessels with sparging stirrers, bubblecolumns or trickle bed columns. The trickle bed can comprise shapedbodies made of, for example, steel, glass, aluminum oxide, silicondioxide, steatite, acid ion exchangers or activated carbon and alsonoble metals such as palladium deposited on activated carbon. In certaincases, it may be advantageous to use a certain amount of an organicphase, e.g. crude hydroformylation product, in the preparation of thecatalyst. For example, the organic phase together with the cobalt(II)salt solution can be passed through the trickle bed. Since the cobaltcarbonyl catalyst has a low solubility in water but a high solubility inorganic media, undesirable cobalt deposits can be avoided in this way.However, preference is generally given to carrying out the preparationof the catalyst in the absence of any organic phase.

[0023] This gives an aqueous solution laden with the cobalt carbonylcatalyst, and this solution is either introduced as such into thereaction zone or the catalyst is separated from it and introduced as gasphase or organic liquid phase into the reaction zone, as is explainedbelow.

[0024] To separate off the cobalt carbonyl catalyst and reformcobalt(II) salts, the output from the reaction zone is appropriatelytreated with oxygen or air in the presence of an aqueous phase. In thisprocedure, the cobalt carbonyl catalyst is decomposed by oxidation andthe cobalt atom is formally converted from the oxidation state −1 to +2and can then be removed by extraction with the aqueous phase. This stepis also referred to as “oxidative cobalt removal” and is described inmore detail below in the context of a preferred embodiment of theprocess of the present invention.

[0025] As an alternative, the output from the reaction zone can also betreated with an aqueous solution containing cobalt(II) ions in theabsence of oxygen, forming a water-soluble complex in the form ofCo[Co(CO)₄]₂ which is then oxidized by means of oxygen or air to givethe uniformly divalent form of cobalt. Such a process is, for example,useful when the cobalt carbonyl catalyst is not to be destroyedquantitatively by oxidation, but part thereof is to be separated offbeforehand in undecomposed form by means of a stripping gas. Thestripping gas treatment of the reaction product can advantageously becombined with the stripping of the cobalt carbonyl catalyst from anaqueous solution in which it is present, as is indicated below for apreferred embodiment of the process of the present invention.

[0026] Suitable catalyst precursors include not only aqueous cobalt(II)salt solutions but also an aqueous solution of a salt of the cobalttetracarbonyl anion, in particular the sodium salt. This can beacidified, for example with sulfuric acid, to produce the cobaltcarbonyl catalyst. To separate off the cobalt carbonyl catalyst andreform the cobalt tetracarbonyl anion, the output from the reaction zonecan be treated with the aqueous solution of a base, e.g. sodiumcarbonate solution, which results in conversion of the hydridocobaltcarbonyl back into a water-soluble salt thereof.

[0027] The above methods of preparing the catalyst give an aqueous phasecomprising the cobalt carbonyl catalyst. The preformed cobalt carbonylcatalyst can be transferred from the aqueous phase into the organicphase outside the reaction zone. Alternatively, the aqueous phasecomprising the cobalt carbonyl catalyst is introduced as such into thereaction zone. In the first case, the cobalt carbonyl catalyst isdissolved in an organic phase comprising the polyalkylenes and theorganic phase laden with the cobalt carbonyl catalyst is introduced intothe reaction zone. To dissolve the cobalt carbonyl catalyst in theorganic phase, the aqueous phase comprising the cobalt carbonyl catalystcan be brought into contact with the organic phase, with the cobaltcarbonyl catalyst being at least partly extracted into the organicphase.

[0028] Suitable apparatuses for the extraction of the cobalt carbonylcatalyst from the aqueous phase into the organic phase are allindustrially customary apparatuses which are suitable for an extractionunder atmospheric pressure or under superatmospheric pressure. Use isadvantageously made of countercurrent extraction apparatuses which canbe filled with packing elements, e.g. Raschig rings, Pall rings or glassspheres, or have labyrinth packing to create a large mass transfer area.As alternatives, apparatuses operating according to the mixer-settlerprinciple or intensively stirred vessels are also suitable.

[0029] The extraction is advantageously carried out using the totalamount of organic phase which is subsequently introduced into thereaction zone, i.e. the total amount of polyalkylene or the mixture ofalkylene and solvents which are additionally used. The flow ispreferably chosen so that a phase ratio of aqueous phase to organicphase of from about 1:1 to 1:50, in particular from 1:10 to 1:20, isobtained.

[0030] The conditions in the catalyst extraction are chosen so that nohydroformylation occurs during the catalyst extraction. In general, atemperature of from 5 to 150° C., preferably from 70 to 100° C., and apressure of from 50 to 400 bar, preferably from 250 to 300 bar, aresuitable. If the cobalt catalyst is prepared by treating an aqueouscobalt(II) salt solution with synthesis gas, pressure and temperatureconditions comparable to those in the preparation of the catalyst arealso suitable for the catalyst extraction.

[0031] In place of a liquid/liquid extraction, it is also possible totreat the aqueous phase comprising the cobalt carbonyl catalyst, in thepresence or absence of the output from the reaction zone which likewisecomprises cobalt carbonyl catalyst, with a stripping gas, in particularsynthesis gas, and to bring the stripping gas laden with the cobaltcarbonyl catalyst into contact with an organic phase comprising thepolyalkylenes, with the cobalt carbonyl catalyst being at least partlyabsorbed in the organic phase.

[0032] As an alternative, an organic phase comprising the polyalkylenesand the aqueous phase comprising the cobalt carbonyl catalyst can beintroduced simultaneously into the reaction zone, with extraction of thecobalt carbonyl catalyst into the organic phase occurring in thereaction zone in this case. For this purpose, the aqueous phasecomprising the cobalt carbonyl catalyst and the organic phase comprisingthe polyalkylenes are introduced into the reaction zone in such a waythat good mixing of the phases occurs and a very high mass transfer areais generated. For introducing the phases, it is possible to use the feeddevices known to those skilled in the art, for example turbulence tubesfilled with packing or mixing nozzles for multiphase systems. The twophases can optionally be introduced together with the synthesis gas viaa line into the reaction zone.

[0033] If the aqueous phase comprising the cobalt carbonyl catalyst isintroduced together with the organic phase into the reaction zone, ithas to be ensured that the aqueous phase does not accumulate in thereaction zone, which can lead to a gradual slowing and possibly completecessation of the hydroformylation reaction. This can be achieved, forexample, by taking off the reaction product at a plurality of points onthe reaction zone or, when using a plurality of reaction zones, at leastthe first reaction zone, e.g. the first reactor of a reactor cascade. Ifthe reaction product is, for example, taken off only at the top of thereactor, the amount of aqueous phase which is introduced into thereaction zone and is necessary to achieve a sufficient catalystconcentration in the reaction zone is sometimes not completelydischarged in dissolved or suspended form with the reaction mixture. Thedenser aqueous phase accumulates near the bottom of the reactor. Forthis reason, reaction product is taken off both at the top of thereactor and also from the bottom region of the reactor in a preferredembodiment. The reaction product from the bottom region generallycomprises from 10 to 100% by volume, in particular from 30 to 50% byvolume, of aqueous phase.

[0034] The organic phase advantageously comprises an organic solvent inaddition to the polyalkylenes. Aromatic or aliphatic hydrocarbons arepreferred as solvents. Examples which may be mentioned are benzene,toluene, xylenes, ethylbenzenes, cyclohexane, paraffin fractions, inparticular linear or branched C₆-C₃₀-alkanes. Preferred solvents areessentially insoluble in water and are readily miscible with thepolyalkylenes and with the cobalt carbonyl catalyst.

[0035] The temperature in the hydroformylation is generally from 100 to250° C., in particular from 120 to 200° C. The reaction is preferablycarried out at a pressure in the range from 150 to 400 bar, inparticular from 200 to 300 bar.

[0036] Suitable pressure-rated reactors for hydroformylation are knownto those skilled in the art. They include the generally customaryreactors for gas/liquid reactions, e.g. tube reactors, stirred vessels,gas recycle reactors, bubble columns, etc., which may be divided byinternals. A suitable reactor is, for example, an upright high-pressurebubble column reactor which may be provided with coaxial tubularinternals. For the purposes of the present invention, a “reaction zone”is the region of a reactor in which appropriate pressure and temperatureconditions prevail and the reactants come into contact with one anotherin such a way that the hydroformylation reaction occurs. To achieve thehighest possible conversions, it can be advantageous to carry out thehydroformylation in at least two successive reaction zones which may belocated in one or more reactors. For the purposes of the presentinvention, a plurality of reaction zones is said to be present whenessentially no backmixing takes place between them. The formation of aplurality of reaction zones in one reactor can be achieved by suitablecascading of the reactor. As an alternative, two or more reactors can beconnected in series in order to carry out the hydroformylation in aplurality of reaction zones. If appropriate, fresh synthesis gas can beintroduced into the second reaction zone or a further reaction zone.Uniform transport of material from the first reaction zone to the secondor further reaction zone is preferably achieved by maintaining aconstant pressure difference of a few bar, e.g. from 2 to 5 bar.

[0037] Synthesis gas is an industrial mixture of carbon monoxide andhydrogen. The composition of the synthesis gas used in the process ofthe present invention can vary within a wide range. The molar ratio ofcarbon monoxide to hydrogen is generally from about 10:1 to 1:10, inparticular from 2.5:1 to 1:2.5. A preferred ratio is from about 40:60 to50:50.

[0038] The process of the present invention is preferably carried out sothat the concentration of the cobalt carbonyl catalyst, calculated ascobalt, is from 0.05 to 1.5% by weight, in particular from 0.1 to 0.5%by weight, based on the organic phase introduced into the reaction zone.

[0039] A preferred embodiment of the process of the present invention isa process in which

[0040] a) an aqueous cobalt(II) salt solution is brought into intimatecontact with synthesis gas to form a cobalt carbonyl catalyst,

[0041] b) the aqueous phase comprising the cobalt carbonyl catalyst isbrought into contact with an organic phase comprising the polyalkylenes,with the cobalt carbonyl catalyst being at least partly extracted intothe organic phase,

[0042] c) the organic phase is hydroformylated by means of synthesis gasat superatmospheric pressure and elevated temperature in the reactionzone,

[0043] d) the output from the reaction zone is treated with oxygen inthe presence of aqueous cobalt(II) salt solution, with the cobaltcarbonyl catalyst being decomposed to form cobalt(II) salts and thelatter being back-extracted into the aqueous phase, and

[0044] e) the aqueous cobalt(II) salt solution is recirculated to stepa).

[0045] The extraction of the cobalt carbonyl catalyst into thepolyalkylene-containing organic phase in step b) can be carried outeither outside the reaction zone or simultaneously with thehydroformylation in the reaction zone, with reference being made to theabove statements to avoid repetition. In view of the lower outlay interms of apparatus, preference is usually given to carrying out thecatalyst extraction in the reaction zone, i.e. the aqueous phase and theorganic phase come into contact with one another only in the reactionzone.

[0046] In the cobalt removal step (step d), the output from the reactionzone is treated with molecular oxygen, usually in the form of air, inthe presence of aqueous weakly acidic cobalt(II) salt solution. In thisstep, the cobalt present in the cobalt carbonyl catalyst is oxidized inaccordance with the following equation from the oxidation state −1 to +2and is removed from the organic phase of the reaction mixture byextraction with the aqueous phase:

2HCO(CO)₄+1.50₂+4H⁺→2Co²⁺+8CO+3H₂O

[0047] In general, the amount of aqueous phase used is from 0.1 to 10times, preferably from 0.1 to 1 times, in particular from 0.5 to 0.9times, the amount of organic phase to be treated, measured in kg/kg. Asa result of this measure, the aqueous phase is present as a dispersephase in the form of small droplets and the organic phase is thenpresent as a water-in-oil emulsion. It has been found to be advantageousto set the phase ratio indicated, since the subsequent separation of thephases is then made substantially easier.

[0048] The cobalt removal is generally carried out at a pH of from 2 to6, preferably from 3 to 4. The pH can be appropriately controlled byaddition of a carboxylic acid, in particular formic acid or acetic acid.The acid content of the aqueous phase should in each case be sufficientto take up all the cobalt in accordance with the above equation.

[0049] It has been found to be advantageous to use the cobalt-depletedcobalt(II) salt solution obtained after preparation and extraction ofthe catalyst as acidic aqueous solution in the cobalt removal step. Theback-extraction of the cobalt(II) salts in the cobalt removal stepresults in an increase in the concentration to essentially the originalcobalt concentration. The aqueous cobalt(II) salt solution obtained inthis way in the cobalt removal step can then be recirculated to thecatalyst preparation step. The concentration of cobalt(II) salts in thecircuit is advantageously chosen so that the cobalt(II) salts remain insolution and do not precipitate. A cobalt(II) concentration in thecircuit of the cobalt(II) salt solution of from 0.5 to 2% by weight ofcobalt has been found to be useful.

[0050] At the same time as it is brought into contact with the acidicaqueous phase, the output from the reaction zone is brought into contactwith molecular oxygen, preferably in the form of air. The amount ofmolecular oxygen is selected so that it is at least twice, preferably2.1 times, the amount of cobalt present in the output from the reactionzone. When air is used, this means that 2.7 standard m³ of air are to beemployed per gram of cobalt. The amount of oxygen preferably does notexceed 2.5 times the stoichiometrically required amount. To carry outthe cobalt removal successfully, it has been found to be useful to bringthe acidic aqueous phase into contact with air before it is brought intocontact with the organic phase. In this way, the aqueous phase becomessaturated with the available oxygen, as a result of which the subsequentoxidation is not restricted by slow mass transfer taking place through agas/liquid interface. The mixing of the aqueous phase and the gaseousphase comprising molecular oxygen can be carried out in any apparatusfor carrying out gas/liquid reactions, e.g. in a bubble column, a mixingsection, an intensively stirred mixing vessel or a two-fluid nozzle.

[0051] Cobalt removal is preferably carried out at elevated temperature.In general, temperatures of from 50 to 150° C., preferably from 100 to120° C., are employed. The treatment can be carried out underatmospheric or superatmospheric pressure. It has been found to beparticularly useful to employ a pressure of more than 1 bar, preferablyfrom 5 to 50 bar. The residence time in the cobalt removal step can bevaried within wide limits.

[0052] Intensive mixing of the organic and aqueous phases is desirableduring cobalt removal. Mixing can be carried out, for example, in astirred vessel, a two-fluid nozzle or a mixing section, e.g. a bed ofpacking elements. Suitable packing elements are Raschig rings, Pallrings, glass spheres and the like.

[0053] Subsequently, it is advantageous firstly to separate the gasphase from the two liquid phases and then to separate the aqueous phasefrom the organic phase. To separate the phases, the mixture of aqueousand organic phases can be introduced into a calming zone and separated.This is advantageously carried out in a horizontal, continuouslyoperated phase separation vessel through which the phases flow at a lowvelocity. Due to the density difference between the phases, the emulsionseparates under the action of gravity, so that the two phases areobtained one on top of the other in coherent form and largely free ofextraneous phases. The aqueous phase obtained is virtually free of theorganic phase, so that the cobalt(II) salt solution can be returned tothe catalyst formation and cobalt removal steps without further work-up.The organic phase is generally obtained as a fine emulsion in whichfinely dispersed droplets of the aqueous phase are present. The fineemulsion is usually very stable and phase separation on the basis of thedensity difference requires a very long residence time. To acceleratethe coalescence of the residual dispersed aqueous phase, one or moremechanical coalescence stages with an integrated or subsequent phaseseparation apparatus are advantageously utilized. Suitable apparatusesare in general separators with coalescence internals such as packingelements, coalescence surfaces or fine-pored elements. The finedispersion is preferably passed from the top downward through a bed ofpacking elements. Wetting of the large surface area of the packingelements results in surface coalescence and at the same time todroplet/droplet coalescence due to droplet movement. In an advantageousembodiment, use is made of a vertical packed column in which the packingelements consist of a material which is wetted by the disperse aqueousphase and the bed of packing elements is flooded by the organic phase.Preference is given to using packed columns filled with packing elementsmade of metal, e.g. metal rings. The large droplets of aqueous phasewhich are formed separate out rapidly and can be taken off as a lowerphase.

[0054] Emulsion breakers are advantageously used in the phaseseparation. Suitable emulsion breakers are, in particular, alkoxylatedcompounds as are customarily used in the petroleum industry to separateoff salt-containing water. These are, for example,

[0055] a) oligoamines, polyamines, oligoimines and polyiminesalkoxylated with propylene oxide and optionally also ethylene oxide,

[0056] b) alkoxylated alkylphenol-formaldehyde resins and

[0057] c) ethylene oxide/propylene oxide block copolymers, and also

[0058] d) their polymeric acrylic esters,

[0059] as are described in DE-A-2 227 546 and DE-A-2 435 713 (a), DE-A-2013 820 (b), DE-A-1 545 215 (c) and DE-A-4 326 772 (d).

[0060] Particular preference is given to using an emulsion breakerobtained by reacting polyethyleneimine having a molecular weight of from10,000 to 50,000 with such amounts of propylene oxide and optionallyalso ethylene oxide that the content of alkoxy units is from 90 to 99%by weight.

[0061] The amount of emulsion breakers which needs to be added toachieve the desired effect is generally from about 0.1 to 100 g/metricton of organic phase used, preferably from 2 to 20 g/metric ton.

[0062] The emulsion breaker is preferably added continuously in dilutedform. Dilution with an inert solvent, e.g. ortho-xylene, aids handlingand metering of the small amount required. The addition isadvantageously carried out together with the addition of the aqueousextraction solution and the air under release of pressure, as a resultof which the emulsion breaker is effectively mixed in.

[0063] A further preferred embodiment of the process of the presentinvention is a process in which

[0064] a) a polyalkylene-containing organic phase laden with a cobaltcarbonyl catalyst is hydroformylated by means of synthesis gas atsuperatmospheric pressure and elevated temperature in the reaction zone,

[0065] b) the output from the reaction zone is admixed with an aqueousacid and stripped by means of a stripping gas in the presence of anaqueous phase comprising a cobalt carbonyl catalyst, with the cobaltcarbonyl catalyst being at least partly entrained by the stripping gasand partly converted into a water-soluble form and extracted into theaqueous phase,

[0066] c) the aqueous phase is treated with oxygen, with thewater-soluble form of the cobalt carbonyl catalyst being decomposed toform cobalt(II) salts,

[0067] d) the aqueous cobalt(II) salt solution is brought into intimatecontact with synthesis gas to form a cobalt carbonyl catalyst and theaqueous phase comprising the cobalt carbonyl catalyst is recirculated tostep b),

[0068] e) the stripping gas laden with the cobalt carbonyl catalyst fromstep b) is brought into contact with a polyalkylene-containing organicphase, with the cobalt carbonyl catalyst being at least partly absorbedin the organic phase, and the organic phase is recirculated to step a).

[0069] As aqueous acid in step b), formic acid is particularly useful.The process according to this embodiment can be carried out in a manneranalogous to the process described in U.S. Pat. No. 5,434,318, which ishereby fully incorporated by reference.

[0070] A further preferred embodiment of the process of the presentinvention is a process in which

[0071] a) an aqueous solution of a salt of the cobalt tetracarbonylanion is acidified to form a hydroformylation-active cobalt carbonylcatalyst,

[0072] b) the aqueous solution comprising the cobalt carbonyl catalystis brought into intimate contact with an organic phase comprising thepolyalkenes, with the cobalt carbonyl catalyst being at least partlyextracted into the organic phase,

[0073] c) the organic phase is hydroformylated in the reaction zone,

[0074] d) the output from the reaction zone is treated with an aqueoussolution of a base to reform the cobalt tetracarbonyl anion, and theaqueous solution is recirculated to step a).

[0075] The process according to this embodiment can be carried out in amanner analogous to the process described in H. Lemke, “Select the BestOxo Catalyst Cycle” Hydrocarbon Processing Petrol. Refiner, 45(2)(February 1966), 148-152.

[0076] The process of the present invention will now be described inmore detail with reference to the accompanying FIGS. 1 to 3.Self-evident details which are not necessary for an understanding of thepresent invention have been left out for reasons of clarity.

[0077]FIG. 1 schematically shows a plant suitable for carrying out theprocess of the present invention with separate extraction stage. Anaqueous cobalt(II) salt solution is fed via line (8 a) into a carbonylformation zone (16) and synthesis gas is fed into this zone via line(2). The output from the carbonyl formation zone (16) is transferred vialine (17) to the extraction zone (18) into which a polyalkylene or amixture of polyalkylene and a solvent is fed at the same time via line(1). The cobalt carbonyl catalyst formed largely goes into thepolyalkylene-containing phase which is then, after phase separation,conveyed via line (3) to the reaction system (4). The aqueous solutionwhich is depleted in cobalt carbonyls and still contains cobalt(II) saltis conveyed via lines (19) and (8) to the cobalt removal step (6). Inthe reaction system (4), which can comprise a plurality of reactors orone reactor with suitable internals, the reaction of the polyalkylenewith synthesis gas takes place under hydroformylation conditions to formhydroformylation products. The output from the reaction system is passedvia line (5) to the cobalt removal step (6) and is treated with air vialine (7) and an aqueous acidic cobalt(II) salt solution via line (8).Here, the oxidation state of the cobalt changes from −1 to +2 and thecobalt is dissolved in the acidic aqueous phase as cobalt(II) salt.Immediately after cobalt removal, an emulsion breaker is added via line(9). The crude product mixture is then conveyed via line (10) to a phaseseparation vessel (11). Here, the gas phase and the two liquid phasesseparate. The unreacted air and the carbon monoxide and hydrogen carriedover from the synthesis stage are discharged via line (12). The aqueousphase which separates out is returned via line (8 a) to the carbonylformation zone (16). After phase separation (11), the organic phase,which still contains small amounts of aqueous phase, is passed via line(13) to a coalescence stage (14), e.g. a packed column filled with metalpacking elements. After the coalesced aqueous phase has been separatedoff, the crude hydroformylation product can be passed via line (15) tofurther work-up.

[0078]FIG. 2 shows an embodiment of the process of the present inventionwithout a separate extraction stage. An aqueous cobalt(II) salt solutionis fed via line (8 a) to a carbonyl formation zone (16) and synthesisgas is fed in via line (2). The output from the carbonyl formation zoneis fed via line (3) to the hydroformylation system (4) which comprisestwo reactors connected in series and into which synthesis gas via line(2) and the polyalkylene or a mixture of polyalkylene and solvent vialine (1) are additionally introduced. The output from the reactionsystem is, as indicated above with reference to FIG. 1, conveyed vialine (5) to the cobalt removal step (6). In addition, an aqueous phasedepleted in cobalt carbonyls is taken off at the bottom of the firstreactor of the hydroformylation system and conveyed via line (20) to thecobalt removal step (6). This discharge can be dispensed with if theaqueous phase which has been depleted in cobalt carbonyls is soluble ordispersible in the hydroformylation mixture. The further work-up iscarried out as described above with reference to FIG. 1, with identicalreference numerals having the same meaning.

[0079]FIG. 3 shows an embodiment of the process of the present inventionin which the preformed cobalt carbonyl catalyst is stripped by means ofa stripping gas and absorbed in the organic phase to be hydroformylated.A cobalt carbonyl catalyst and polyalkylene-containing organic phase arefed via line (1) into the reactor (3) and synthesis gas is fed into thereactor via line (2). In the reactor (3), the hydroformylation reactiontakes place at elevated temperature and superatmospheric pressure. Thereaction product is discharged via line (4), and an aqueous solution ofa carboxylic acid such as formic acid is added to it via line (6). Thereaction product which has been treated in this way is treated with astripping gas, e.g. synthesis gas, in the stripper (7) where part of thevolatile cobalt carbonyl catalyst is carried out by the stripping gasand taken off via line (9). At the bottom of the stripper (7), aheterogeneous mixture of organic reaction product and the aqueous phasecomprising dissolved cobalt compounds is taken off and conveyed to aphase separation vessel (10). The organic phase is taken off via line(11) and passed to further work-up. The aqueous phase is conveyed vialine (12) to the cobalt removal apparatus (13) where it is treated withan oxygen-containing gas such as air and the soluble cobalt compoundsare converted into cobalt(II) salts. The treated aqueous solution isconveyed via line (15) to an evaporator (16) where a more highlyconcentrated cobalt(II) salt solution and an aqueous carboxylic acidsolution are obtained. The aqueous carboxylic acid solution can berecirculated via line (6) to acidify the organic reaction product fromthe hydroformylation. The concentrated cobalt(II) salt solution isconveyed via line (17) to the cobalt carbonyl generator (20) into whichsynthesis gas is additionally fed via line (18). In addition, a smallamount of the crude hydroformylation product from which the cobalt hasbeen removed is advantageously fed via line (19) to the cobalt carbonylgenerator (20). In the cobalt carbonyl generator (20), a cobalt carbonylcatalyst is prepared from the dissolved cobalt(II) salts and is conveyedvia line (5) to the stripper (7). The stripping gas laden with thecobalt carbonyl catalyst from the stripper (7) is conveyed via line (9)to the absorber (21) into which a polyalkylene-containing organic phaseis fed via line (22). The stripping gas depleted in the cobalt carbonylcatalyst is fed back to the stripper (7) via line (8). The organic phaseladen with the cobalt carbonyl catalyst is fed via line (1) to thereactor (3).

[0080] The process of the present invention is illustrated by thefollowing examples.

EXAMPLES Comparative Example 1

[0081] Use of Aqueous Cobalt Salt Solution as Hydroformylation Catalyst

[0082] 3660 kg/h of a mixture of 1940 kg/h of polyisobutenes and 1720kg/h of a C₁₀-C₁₄ paraffin fraction were fed into a hydroformylationreactor system. At the same time, 300 kg/h of aqueous acidic cobaltformate solution whose pH had been adjusted to about 3.4 by means offormic acid and which contained 1.3% by eight of cobalt were introducedinto the system.

[0083] In the hydroformylation reactor system, the hydroformylationreaction took place at from 180 to 185° C. The reactor pressure of about270 bar was kept constant by introduction of the necessary amount ofsynthesis gas.

[0084] After passing through the reactor section, the product wasdepressurized into a cobalt removal zone. Here, the pressure was reducedfrom about 270 bar to 20 bar. In addition, 2600 kg/h of cobalt saltsolution of the abovementioned composition and 17 kg/h of air were fedinto the cobalt removal zone. Immediately downstream of the outlet fromthe cobalt removal step, an emulsion breaker was added as dilutesolution in such an amount that the concentration of breaker was 12 gper metric ton of reaction mixture. The emulsion breaker was apolyethyleneimine modified with propylene oxide (molecular weight of thepolyethylenimine used for the preparation: about 20,000; content ofpropoxy units: 99% by weight, cf. WO 98/12235).

[0085] In a calming zone, 200 kg/h of depressurization gas wereseparated off and discharged into a collector system.

[0086] The liquid phases were separated from one another. The aqueousphase was largely free of organic constituents and the content of cobaltcarbonyls was only 0.05% by weight.

[0087] The organic phase still contained about 0.7% by weight ofextraneous phase. The further work-up was carried out as described in WO98/12235. 93% of the polyisobutylene used had been reacted. 62% of thepolyisobutene reacted had been converted into the desired productspolyisobutylaldehyde, polyisobutyl alcohol or polyisobutyl ester. Thepolyisobutene conversion and the yields of polyisobutenealdehyde,polyisobutyl alcohol or polyisobutyl ester were determined by columnchromatography and by determination of the parameters with which thoseskilled in the art are familiar.

Example 2

[0088] Use of Organic Cobalt Carbonyl Solutions as HydroformylationCatalyst

[0089] 208 kg/h of aqueous acidic cobalt formate solution whose pH hadbeen adjusted to 3.4 by means of formic acid and which contained 1.3% byweight of cobalt were fed into a precarbonylation reactor. Theconversion of the cobalt formate into cobalt carbonyls was carried outat 95° C. and 280 bar by means of a gas mixture of 40% by volume of COand 59% by volume of H₂ (+1% of inert gases). Essentially all the gasnecessary for carrying out the hydroformylation was passed through theprecarbonylation reactor. This had a volume of 2.3 m³ and was filledwith activated carbon. After passage through the precarbonylationreactor, 70% of the available cobalt had been converted intohydridocobalt carbonyl.

[0090] The output from the precarbonylation reactor was passed withoutdepressurization to an extraction zone into which 3660 kg/h of a mixtureof 1940 kg/h of polyisobutene and 1720 kg/h of a C₁₂-C₁₄ paraffinfraction were additionally introduced. In the extraction zone,consisting of a mixing zone and a calming zone, the cobalt carbonylswere largely transferred from the aqueous phase into the organic phasecomprising the polyisobutene and the C₁₂-C₁₄ paraffin fraction. The 185kg/h of aqueous phase depleted in cobalt carbonyls were passed to thecobalt removal step.

[0091] The 3700 kg/h of organic phase laden with cobalt carbonyls werefed to the hydroformylation system. The reaction system had a reactionvolume of 21.7 m³, so that the space velocity through the reactionsystem was 0.17 kg/l*h. In the reaction system, the hydroformylationreaction took place at 181° C. The reaction pressure of 270 bar was keptconstant by introduction of the necessary amount of synthesis gas whichhad been taken from the precarbonylation zone.

[0092] After passage through the reaction section, the product wasdepressurized into a cobalt removal zone. Here, the pressure was reducedfrom 270 to 20 bar. In addition, 2300 kg/h of cobalt salt solution ofthe abovementioned composition and 9.5 kg/h of air, which had beenintensively mixed in a two-fluid nozzle prior to entering the cobaltremoval zone, were fed into the cobalt removal zone and then passedthrough a bubble column at a mean residence time of about 2 minutes. Atemperature of 115° C. was established. Immediately downstream of theoutlet from the cobalt removal zone, an emulsion breaker was added as adilute solution in such an amount that the concentration of breaker was420 mg per metric ton of reaction mixture. The emulsion breaker was apolyethylenimine modified with propylene oxide as described in WO98/12235.

[0093] After the mixing section, 260 kg/h of depressurization gas wereseparated off in a calming zone and discharged into a collector system.The liquid phases were separated from one another. The aqueous phase waslargely free of organic constituents and the content of cobalt carbonylswas only 0.05% by weight. The organic phase still contained about 0.7%by weight of extraneous phase and the cobalt content was 10 ppm. Thefurther work-up was carried out as described in WO 98/12235.

[0094] 92% of the polyisobutene used had been reacted. 90% of thepolyisobutene reacted had been converted into the desired productspolyisobutyl aldehyde, polyisobutyl alcohol or polyisobutyl ester. Thepolyisobutene conversion and the yields of polyisobutenealdehyde,polyisobutyl alcohol or polyisobutyl ester were determined by columnchromatography and by determination of parameters.

Example 3

[0095] Use of Aqueous Cobalt Carbonyl Solutions as HydroformylationCatalyst

[0096] 208 kg/h of aqueous acidic cobalt formate solution whose pH hadbeen adjusted to 3.4 by means of formic acid and which contained 1.3% byweight of cobalt were fed into the above-described precarbonylationreactor. The conversion of the cobalt formate into cobalt carbonyls wascarried out at 95° C. by means of a gas mixture of 40% by volume of COand 59% by volume of H₂ (+1% of inert gases). Essentially all the gasnecessary for carrying out the hydroformylation was passed through theprecarbonylation reactor. After passage through the precarbonylationreactor, 70% of the available cobalt had been converted intohydridocobalt carbonyl. The output from the precarbonylation reactor wasconveyed directly to the hydroformylation system.

[0097] In addition, 3660 kg/h of a mixture of 1940 kg/h of polyisobuteneand 1720 kg/h of a C₁₀-C₁₄ paraffin fraction were introduced into thehydroformylation reaction system. The reactor system had a reactionvolume of 21.7 m³, so that the space velocity through the reactionsystem was 0.17 kg/l*h.

[0098] In the reaction system, the hydroformylation reaction took placeat 181° C. The reaction pressure of 270 bar was kept constant byintroduction of the necessary amount of synthesis gas. At the bottom ofthe first reactor of the reaction system, 185 kg/h of an aqueoussolution depleted in cobalt carbonyls were taken off and passed to thecobalt removal step.

[0099] After passage through the reaction section, the product wasdepressurized into a cobalt removal zone. Here, the pressure was reducedfrom 270 bar to 20 bar. In addition, 2300 kg/h of cobalt salt solutionof the abovementioned composition and 9.5 kg/h of air, which had beenintensively mixed in a two-fluid nozzle prior to entering the cobaltremoval zone, were fed into the cobalt removal zone and then passedthrough a bubble column at a mean residence time of about 2 minutes. Atemperature of 115° C. was established. Immediately downstream of theoutlet from the cobalt removal zone, an emulsion breaker was added as adilute solution in such an amount that the concentration of breaker was420 mg per metric ton of reaction mixture. The emulsion breaker was apolyethylenimine modified with propylene oxide as described in WO98/12235.

[0100] After the mixing section, 360 kg/h of depressurization gas wereseparated off in a calming zone and discharged into a collector system.The liquid phases were separated from one another. The aqueous phase waslargely free of organic constituents and the content of cobalt carbonylswas only 0.05% by weight. The organic phase still contained about 0.7%by weight of extraneous phase and the cobalt content was 10 ppm. Thefurther work-up was carried out as described in WO 98/12235.

[0101] 88% of the polyisobutene used had been reacted. 90% of thepolyisobutene reacted had been converted into the desired productspolyisobutyl aldehyde, polyisobutyl alcohol or polyisobutyl ester. Thepolyisobutene conversion and the yields of polyisobutenealdehyde,polyisobutyl alcohol or polyisobutyl ester were determined by columnchromatography and by determination of parameters.

[0102] The yield of the desired polyisobutenealdehyde, polyisobutylalcohol and polyisobutyl ester in both the examples 2 and 3 according tothe present invention using cobalt carbonyl preformed outside thereaction zone was considerably higher than that in the comparativeexample 1 in which an aqueous cobalt formate solution was introducedinto the reaction system and cobalt carbonyl formation took place onlyin the reaction system.

We claim:
 1. A process for the continuous hydroformylation ofessentially monounsaturated polyalkylenes having from 30 to 700 carbonatoms, in which i) a hydroformylation-active cobalt carbonyl catalyst isprepared from a catalyst precursor dissolved in an aqueous phase in theabsence of the polyalkylenes, ii) the polyalkylenes are hydroformylatedby means of synthesis gas in the presence of the cobalt carbonylcatalyst in a reaction zone, iii) the cobalt carbonyl catalyst isseparated from the output from the reaction zone with at least partialreformation of the catalyst precursor and the catalyst precursor isrecirculated to step i).
 2. A process as claimed in claim 1 in which thecobalt carbonyl catalyst is dissolved in an organic phase comprising thepolyalkylenes and the organic phase laden with the cobalt carbonylcatalyst is introduced into the reaction zone.
 3. A process as claimedin claim 2 in which the cobalt carbonyl catalyst is dissolved in theorganic phase by bringing an aqueous phase comprising the cobaltcarbonyl catalyst into contact with the organic phase, with the cobaltcarbonyl catalyst being at least partly extracted into the organicphase.
 4. A process as claimed in claim 2 in which the cobalt carbonylcatalyst is dissolved in the organic phase by treating an aqueous phasecomprising the cobalt carbonyl catalyst with a stripping gas andbringing the stripping gas laden with the cobalt carbonyl catalyst intocontact with the organic phase, with the cobalt carbonyl catalyst beingat least partly absorbed in the organic phase.
 5. A process as claimedin claim 1 in which an aqueous phase comprising the cobalt carbonylcatalyst and an organic phase comprising the polyalkylenes areintroduced simultaneously into the reaction zone.
 6. A process asclaimed in any of the preceding claims in which the catalyst precursoris a cobalt(II) salt and the cobalt carbonyl catalyst is prepared bytreating the catalyst precursor with synthesis gas.
 7. A process asclaimed in claim 3 or 5 in which a) an aqueous cobalt(II) salt solutionis brought into intimate contact with synthesis gas to form a cobaltcarbonyl catalyst, b) the aqueous phase comprising the cobalt carbonylcatalyst is brought into contact with an organic phase comprising thepolyalkylenes, with the cobalt carbonyl catalyst being at least partlyextracted into the organic phase, c) the organic phase ishydroformylated by means of synthesis gas at superatmospheric pressureand elevated temperature in the reaction zone, d) the output from thereaction zone is treated with oxygen in the presence of aqueouscobalt(II) salt solution, with the cobalt carbonyl catalyst beingdecomposed to form cobalt(II) salts and the latter being back-extractedinto the aqueous phase, and e) the aqueous cobalt(II) salt solution isrecirculated to step a).
 8. A process as claimed in claim 4 in which a)a polyalkylene-containing organic phase laden with a cobalt carbonylcatalyst is hydroformylated by means of synthesis gas atsuperatmospheric pressure and elevated temperature in the reaction zone,b) the output from the reaction zone is admixed with an aqueous acid andstripped by means of a stripping gas in the presence of an aqueous phasecomprising a cobalt carbonyl catalyst, with the cobalt carbonyl catalystbeing at least partly entrained by the stripping gas and partlyconverted into a water-soluble form and extracted into the aqueousphase, c) the aqueous phase is treated with oxygen, with thewater-soluble form of the cobalt carbonyl catalyst being decomposed toform cobalt(II) salts, d) the aqueous cobalt(II) salt solution isbrought into intimate contact with synthesis gas to form a cobaltcarbonyl catalyst and the aqueous phase comprising the cobalt carbonylcatalyst is recirculated to step b), e) the stripping gas laden with thecobalt carbonyl catalyst from step b) is brought into contact with apolyalkylene-containing organic phase, with the cobalt carbonyl catalystbeing at least partly absorbed in the organic phase, and the organicphase is recirculated to step a).
 9. A process as claimed in any ofclaims 1 to 5 in which the catalyst precursor is a salt of the cobalttetracarbonyl anion and the cobalt carbonyl catalyst is prepared byacidification of the catalyst precursor.
 10. A process as claimed inclaim 3 or 5 in which a) an aqueous solution of a salt of the cobalttetracarbonyl anion is acidified to form a hydroformylation-activecobalt carbonyl catalyst, b) the aqueous solution comprising the cobaltcarbonyl catalyst is brought into intimate contact with an organic phasecomprising the polyalkenes, with the cobalt carbonyl catalyst being atleast partly extracted into the organic phase, c) the organic phase ishydroformylated in the reaction zone, d) the output from the reactionzone is treated with an aqueous solution of a base to reform the cobalttetracarbonyl anion, and the aqueous solution is recirculated to stepa).
 11. A process as claimed in any of the preceding claims, wherein thehydroformylation is carried out in at least two successive reactionzones.
 12. A process as claimed in any of claims 2 to 11 in which theorganic phase comprises an inert solvent.
 13. A process as claimed inany of the preceding claims in which homopolymers or copolymers ofisobutene are used as polyalkylene.